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It’s peak time in the computed tomography (CT) department. Professor Elmar Merkle can tell immediately that one of the rooms is being used to treat a patient from the intensive care unit. “That looks like a CT-guided intervention,” explains Merkle, who is Head of Radiology and Nuclear Medicine at University Hospital Basel. In another treatment room, medical staff are wearing masks and additional protective clothing due to the risk of infection because the patient has MRSA, a strain of antibiotic-resistant Staphylococcus. Things are much more quiet two corridors away at two specific magnetic resonance imaging (MRI) scanners, which are primarily used for research studies. Here, there is one system with a 0.55-Tesla field strength as well as a 3-Tesla scanner – and, hidden amongst the electric cables, there are also measurement devices that continuously measure the power consumption of the two systems. 

The Department of Radiology requested specially that these measurement units be installed in order to record the power consumption of each system twice a second – not just here, but for all imaging modalities, including every clinical MRI scanner and other large device in the department. This was an unusual request: “For a long time, no one knew how much energy MRI and CT scanners needed,” says Merkle, and it’s only thanks to his team’s work that this is no longer the case. “It’s paradoxical,” says Tobias Heye, Senior Physician in Merkle’s department and the instigator of these energy measurements. “Today, you’ll find an energy-efficiency label on every TV and coffee machine, but the energy consumption of large imaging devices simply wasn’t a topic of discussion.”

Nowadays, healthcare also has a responsibility to become more carbon-conscious and energy-efficient. Indeed, the global healthcare system is responsible for no less than 4.4 percent of total CO² emissions worldwide. If healthcare were a country, it would come fifth in the list of the largest CO² producers, as Merkle often explains in talks. He believes it is important to reduce this negative impact. “As I see it, we physicians have a responsibility not only to our own patients, but also to society as a whole: We should help to build a world that’ll still be worth living in tomorrow.” 

Merkle has already embarked on these efforts in his own department, working with his team to analyze the energy profile of imaging techniques in detail. To do so, the team used not only the monitoring of energy usage but also data from the radiology information system, as well as the internal log files of systems provided by Siemens Healthineers. 

These data clearly showed which device processes were responsible for the energy consumption measured. These data enabled the team to determine that, on average, an MRI scanner uses as much power as 30 single-family homes, assuming there are four people per household. Likewise, PET/CT scanners and angiography systems each consume the equivalent of ten single-family households, while a CT scanner is equivalent to six households. The lowest consumption – equivalent to half a home – is that of compact ultrasound scanners, but these devices are also the most numerous, with around 150 of them at the University Hospital Basel alone. “If we factor in all of our equipment, including six MRI scanners, nine angiography systems, and five CT scanners, then we use the same power as 500 to 600 single-family homes. That’s like a small village!” says Merkle, nodding emphatically. This is clearly very important to him.

Back in 2020, the publication of these results didn’t gain much traction. Then came the Ukraine war, and energy prices suddenly shot up in Europe. For example, the University Hospital Basel paid some 17 million Swiss francs more for power in 2023 than it did in recent years. “The energy crisis has brought a certain urgency to the issue,” says Merkle. 

With this in mind, it’s good news that there is one surprisingly simple way to reduce power consumption in imaging, according to Merkle: “Turn the devices off overnight. Period.” Indeed, one finding of Merkle’s analysis was that the systems consume most of their power during idle periods, when they are switched on but not recording any images. For instance, in the gaps between patients during the day and overnight, CT scanners use more electricity in total than they do for the scans themselves. Similar is true of MRI scanners: Although the cooling systems for their magnets need to run continuously, Merkle says that an MRI scanner can also be put in a lower energy state overnight without affecting patients. In the morning, the scanners can then be ready for operation again in 15 minutes. 

“Depending on the workflow, it might even make sense to switch the devices off over lunch.” This approach is already used for angiography systems at the University Hospital Basel without causing any problems, as the units are on and ready for the next patient within three minutes – fast enough even for time-sensitive emergencies.

Merkle wishes that imaging departments at other hospitals, as well as other departments, would make a conscious effort to find this sweet spot – and he hopes that awareness of energy efficiency will persevere even after the energy crisis subsides. “Because if I save money thanks to more energy-efficient imaging, I can put that money to sensible use – for example, to employ more nursing or technical staff – and thereby alleviate the shortage of skilled workers, so that I can work more sustainably overall.” 

The head of department is in regular contact with Siemens Healthineers regarding energy consumption in medical imaging. For him, one key development was the “Eco Power Mode” for MRI scanners, which manages cooling more energy-efficiently during idle periods. His measurements indicate that this can save the equivalent energy of two single-family households – per system. That being said, Merkle wishes manufacturers would generally work harder to reduce the power consumption of their systems, such as the relatively high energy consumption of MRI scanners or PET components in PET/CT systems while idle. He is certain of one thing: “When the big industry players make energy efficiency a priority, the sky’s the limit.”